In vehicle airbag devices; e.g., a side airbag, a bag is deployed between a passenger and a side wall to which a door is provided. There are known side airbags, such as disclosed in Japanese Patent No. 3330032, wherein, when a lid corresponding to an outlet of a rectangular box in which the bag is housed is pushed open by the bag, two tear lines formed in the lid rupture as the bag deploys and opens.
In another example of a side airbag, a box in which a bag is housed and a holder into which the box has been fitted open in a consecutive manner. Specifically, there are known side airbags, such as disclosed in Japanese Patent No. 3752527, wherein an outlet wall of the box in which the bag is housed begins to open as a result of the deployment of the bag, whereupon a front wall of the holder ruptures on being pushed by the outlet wall, whereby the bag opens.
However, the side airbags disclosed in Japanese Patent No. 3330032 and Japanese Patent No. 3752527 are problematic in that an outlet wall, a front wall, and a lid corresponding to an outlet all rupture; and the pressing load (resistance) increases.
In side airbags, when significant resistance is experienced in opening the lid or outlet wall, the shape of the deployed airbag will vary widely depending upon the configuration in which the vehicle deforms.